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UTRECHT, Netherlands — Every child who’s ever been fascinated by dinosaurs has wondered: Was it the asteroid or the volcanoes that spelled doom for Earth’s most magnificent creatures? Now, an international team of scientists has uncovered compelling evidence that may finally settle this prehistoric whodunit, revealing a complex story of climate chaos that preceded one of history’s greatest mass extinctions.
In a groundbreaking study published in Science Advances, researchers have discovered that while massive volcanic eruptions did trigger dramatic climate changes before the dinosaurs’ extinction, these effects had already dissipated by the time the fatal asteroid struck Earth. This finding could revolutionize our understanding of one of paleontology’s most enduring mysteries.
The study reveals that ancient volcanic activity caused global temperatures to swing wildly – first warming by about 3 degrees Celsius over 100,000 years, then plunging by up to 5 degrees Celsius in less than 10,000 years before returning to warmer conditions. These temperature changes occurred roughly 30,000 years before the Cretaceous-Paleogene extinction event 66 million years ago, when about 75% of plant and animal species – including all non-avian dinosaurs – vanished from Earth.
“These volcanic eruptions and associated CO2 and sulfur release would have had drastic consequences for life on earth,” says Lauren O’Connor at Utrecht University in a media release. “But these events happened millennia before the meteorite impact and probably played only a small part in the extinction of dinosaurs.”
The culprit behind these temperature swings was the Deccan Traps, a vast region of volcanic rock in western India that formed through a series of massive eruptions. These eruptions released enormous amounts of carbon dioxide, causing long-term warming, and sulfur dioxide, which led to brief but intense cooling periods when converted to sulfate aerosols in the atmosphere.
To uncover this ancient climate record, researchers analyzed fossilized peat (known as lignite) from two sites in North Dakota and Colorado, separated by about 750 kilometers (466 miles). These sites preserved a detailed record of temperature changes through bacterial remains that adjusted their cellular membranes based on environmental conditions – essentially creating a prehistoric thermometer.
“By analyzing the composition of these molecules preserved in ancient sediments… we were able to create a detailed ‘temperature timeline’ for the years leading up to the dinosaur extinction, which we can compare to the fossil record to understand the relative timing of events,” O’Connor explains.
What makes this discovery particularly significant is that it shows Earth’s climate had stabilized well before the asteroid impact.
“By comparison, the impact from the asteroid unleashed a chain of disasters, including wildfires, earthquakes, tsunamis, and an ‘impact winter’ that blocked sunlight and devastated ecosystems. We believe the asteroid ultimately delivered the fatal blow,” concludes Rhodri Jerrett at the University of Manchester.
Paper Summary
Methodology
The researchers analyzed ancient peat deposits that had turned to lignite (a type of coal) over millions of years. They extracted specific molecules called branched glycerol dialkyl glycerol tetraethers (brGDGTs) that were created by bacteria living in the ancient peat. These bacteria modified their cell membranes depending on temperature, creating a natural temperature record that was preserved in the rock. By measuring the different forms of these molecules, the team could calculate the average annual air temperature from millions of years ago.
Key Results
The study found three distinct temperature phases in the last 100,000 years before the extinction: first, a warming trend of about 3 degrees Celsius; second, a sharp cooling of 2-5 degrees Celsius starting around 30,000 years before the extinction; and finally, a return to warmer temperatures. These changes were recorded at both study sites, suggesting they reflected regional or global climate patterns rather than local variations.
Study Limitations
The method used can only provide approximate temperature readings with an error margin of plus or minus 4.7 degrees Celsius. The peat deposits might also show a dampened temperature signal because water in the peat could have buffered temperature changes, and plant roots might have mixed older and newer organic material. This means the actual temperature swings might have been more extreme than measured.
Discussion & Takeaways
The research demonstrates that while volcanic activity caused significant climate changes, these weren’t catastrophic enough to cause mass extinction. The study helps clarify the relative roles of volcanic activity and the asteroid impact in the extinction event. It suggests that while volcanic activity stressed ecosystems, most species could adapt to these changes. The asteroid impact, occurring later, was likely the primary cause of the mass extinction.
Funding & Disclosures
The study was funded by the UK Natural Environment Research Council and the Netherlands Earth System Science Centre, with additional support from the National Science Foundation. The researchers declared no competing interests that might have influenced their work.
